The present invention generally relates to methods and apparatuses for differentiating simultaneous and sequential key strokes, and more particularly to a method and an apparatus for differentiating simultaneous and sequential key strokes made on an input device when inputting information to a computer or the like.
Conventionally, a single key stroke on a keyboard inputs character, symbol and numeric information to a computer or the like. In addition, in order to minimize the number of keys on the keyboard and enable a larger amount of character, symbol and numeric information to be input from the keyboard, an input is also made by a combination of one key and a control key such as a shift key or a voiced sound key. When making the input by such a key combination, the key stroke of one key and the key stroke of the control key are made simultaneously.
On the other hand, the simultaneous and sequential key strokes are conventionally differentiated in the following manner. That is, it is judged that the key stroke K.sub.1 is a part of sequential key strokes when a time T.sub.L elapses from a time when the key K.sub.1 is first pushed. Similarly, it is judged that the key stroke K.sub.2 is a part of sequential key strokes when a time T.sub.L elapses from a time when the key K.sub.2 is first pushed. The time T.sub.L is a fixed parameter used for detecting simultaneous key strokes, and is normally set to 100 msec. On the other hand, it is judged that the key strokes of the keys K.sub.1 and K.sub.2 are simultaneous if the second key K.sub.2 is pushed before the time T.sub.L elapses from the time when the first key K.sub.1 is pushed. In other words, the key strokes are judged as being simultaneous if the keys K.sub.1 and K.sub.2 are pushed within the time T.sub.L.
FIGS. 1 and 2 are diagrams for explaining the operation of differentiating the simultaneous and sequential key strokes. As shown in FIG. 2, it is detected that the key stroke K.sub.1 is a part of the sequential key strokes if the time T.sub.L elapses from the time when the key K.sub.1 is pushed and the key K.sub.2 is not pushed during this time T.sub.L. The simultaneous key strokes of the keys K.sub.1 and K.sub.2 are detected if the key K.sub.2 is pushed before the time T.sub.L elapses from the time when the key K.sub.1 is pushed.
However, as may be seen from FIG. 2, a differentiation of the simultaneous and sequential key strokes is conventionally not made if both times T.sub.1 and T.sub.2 fall within the time T.sub.L, where T.sub.1 is the time difference between the time when the key K.sub.1 is pushed and the time when the key K.sub.2 is pushed, and T.sub.2 is the time difference between the time when the key K.sub.2 is pushed and the time when the key K.sub.1 is released. That is, T.sub.2 is the time during which both the keys K.sub.1 and K.sub.2 are held pushed.
Accordingly, the key strokes are all judged as being simultaneous key strokes if both the times T.sub.1 and T.sub.2 are shorter than the time T.sub.L. In this case, there are problems in that an input error may occur in response to the key strokes which are made, and that the differentiating accuracy of the key strokes is poor.